Field of the Invention
The present invention relates to a developing device used in an electrophotographic image forming apparatus, a process cartridge including the developing device, and the electrophotographic image forming apparatus.
The electrophotographic image forming apparatus forms an image on a recording material according to an electrophotographic image forming process. The electrophotographic image forming apparatus is, for example, a copying machine, a printer (e.g., laser beam printer, LED printer), a facsimile machine, or a word processor.
The developing device visualizes an electrostatic image formed on an electrophotographic photosensitive member (photosensitive member) by the electrophotographic image forming process using developer.
The process cartridge generally includes a photosensitive member and process units, which act on the photosensitive member, in an integrated manner. The process cartridge is removable from the apparatus main body of the electrophotographic image forming apparatus. The process units include, for example, a charging unit, a developing unit, and a cleaning unit. According to the present invention, the process cartridge is a cartridge including a photosensitive member and at least a developing device in an integrated manner, and is removable from the apparatus main body of the electrophotographic image forming apparatus.
Description of the Related Art
Among the electrophotographic image forming apparatuses using the electrophotographic image forming process, there is an image forming apparatus employing the process cartridge method. The electrophotographic image forming apparatus employing the process cartridge method uses a cartridge removable from the apparatus main body of the electrophotographic image forming apparatus. The cartridge includes a photosensitive member and process units that act on the photosensitive member in an integrated manner. Since the user of such an image forming apparatus can perform maintenance of the apparatus by herself/himself without help from a service engineer, operability is significantly improved.
Generally, as development methods of a developing device of an electrophotographic image forming apparatus, there are methods such as a contact development method and a contactless development method. Whereas the development is performed in a state where a developer bearing member contacts the photosensitive member according to the contact development method, the development is performed in a state where a predetermined space exists between the developer bearing member and the photosensitive member according to the contactless development method. Further, as a method for supplying developer to the developer bearing member, Japanese Patent Application Laid-Open No. 2010-009021 discusses a method that supplies developer from a developer storage chamber to a development chamber by a conveyance member. According to this method, the developer is supplied via an opening formed in a partition that separates the developer storage chamber storing developer and the development chamber provided with the developer bearing member.
According to this method, the conveyance member is attached to a rotating shaft, which is rotatable and located in the developer storage chamber. The developer supplied to the development chamber by the conveyance member is rubbed by a developer supplying member for supplying developer to the developer bearing member, and a developer regulation member, which controls the amount of developer bore by the developer bearing member, and bore by the developer bearing member. The developer which is not bore by the developer bearing member is accumulated in the development chamber. When the amount of the accumulated developer reaches a predetermined amount, the developer is spilled out from the development chamber via the above-described opening, and returns to the developer storage chamber. The developer inside the development chamber may be deteriorated due to friction. However, if the developer is returned from the development chamber to the developer storage chamber and is mixed with the developer in the developer storage chamber, the deteriorated developer inside the development chamber will not be accumulated to an amount more than an acceptable level, and the developer in the development chamber and the developer inside the containing chamber can circulate.
On the other hand, in order to provide remaining developer level information to the user and prompt the user to smoothly replace the process cartridge, the amount of developer that remains in the developer storage chamber is detected. As one method for detecting the amount of developer, there is a method called developer amount detection method using light transmission. This method is discussed in Japanese Patent Application Laid-Open Nos. 2010-009021 and 2003-131479.
According to this method, detection light emitted from a light emitting unit, such as a light-emitting diode (LED), attached to, for example, the main body of the electrophotographic image forming apparatus is guided to the inside of the developer storage chamber via a light guide and a light transmission window attached to the developer storage chamber. The detection light incident on the inside of the developer storage chamber is output from the developer storage chamber via the light transmission window (or, for example, via a reflection mirror) depending on the amount of developer in the developer storage chamber. Then, by a light guide attached to the developer storage chamber, the detection light is guided to a light-receiving unit such as a photo transistor attached to the apparatus main body.
According to the method discussed in Japanese Patent Application Laid-Open No. 2010-009021, the detection light is blocked by the developer scooped by the conveyance member provided in the developer storage chamber in a rotatable manner. Since the transmission time of light is increased when the amount of developer that remains inside the developer storage chamber is reduced, the amount of developer in the developer storage chamber can be estimated according to the transmission time of the detection light.
If the rotation speed of the conveyance member is increased to realize high speed printing of the electrophotographic image forming apparatus, the developer may be dumped from the conveyance member when it is conveyed and scattering of the developer may occur inside the developer storage chamber. If the developer is scattered inside the developer storage chamber, the detection light will be blocked by the scattered developer, and the detection accuracy of the developer amount detection method using light transmission may be reduced.
According to the method discussed in Japanese Patent Application Laid-Open No. 2010-009021, a receiving member configured to receive the developer falling from the conveyance member is provided on a rotating shaft disposed in the developer storage chamber. The receiving member prevents the developer from being scattered in the developer storage chamber.
As described in the exemplary embodiments below, the length of the receiving member made of a flexible sheet member, such as the one discussed in Japanese Patent Application Laid-Open No. 2010-009021, can be increased so that the receiving member slides over the inner wall surface of the developer storage chamber. The length of the receiving member is the length in the rotation radial direction of the rotating shaft.
However, in this case, the opening formed in the partition that separates the developer storage chamber and the development chamber is temporarily blocked by the receiving member each time the rotating shaft rotates, and the travel of the developer from the development chamber to the developer storage chamber via the opening may be blocked. Thus, the circulation of the developer between the development chamber and the developer storage chamber may be temporarily blocked. If the circulation of the developer is temporarily blocked, due to friction between the developer and the developer supplying member or the developer regulation member, deterioration of the developer accumulated in the development chamber may be accelerated. This may adversely affect the image.